Conventionally, there are power conversion devices used as devices for charging a battery that serves as a power supply to an electronic control unit (ECU: Electronic Control Unit), such as an engine controller. This type of power conversion device rectifies an output of an AC generator driven by an engine, thereby generating a DC voltage to charge the battery.
According to power conversion devices of related art, a battery is discharged by dark current, such as leakage current or standby current flowing through the electronic control unit during a period in which the AC generator is not generating power, so that a battery voltage decreases in some cases. Patent Document 1 discloses a technique for blocking such dark current.
FIG. 5 is a diagram for explaining a conventional device disclosed in Patent Document 1. According to this conventional device, when an AC generator 201 is generating power, an electronic control unit (ECU) 205 turns on a battery relay 203. In this case, an AC output of the AC generator 201 is converted into a desired DC power by a regulator 202 that is a power conversion device. This DC power is supplied to a battery 204 through a battery relay 203, so that the battery 204 is charged. Additionally, the regulator 202 also provides power supply to the electronic control unit 205.
On the other hand, when the AC generator 201 is not generating power, that is, when the battery 204 is not in the charging state, the electronic control unit 205 turns off the battery relay 203. Thereby, the battery 204 is electrically disconnected from the electronic control unit 205, so that dark current flowing from the battery 204 to the electronic control unit 205 is cut off.
In addition to the above-described conventional device, in a system having a main switch such as a key switch, a configuration may be such that dark current is cut off by the main switch.